The present invention relates to a three dimensional shaped fiber sheet and, in particular, relates to a three dimensional shaped carpet used for an automobile and a method for manufacturing the carpet.
A carpet is used as a mat for an automobile such as a passenger car, a truck, a bus and the like. A carpet base material of such a carpet is classified roughly into a tufted type and a needle punched type.
The tufted type of a carpet base material is manufactured by stitching a base fabric to provide fiber loops (or piles) on a front surface of the base fabric so as to form tufts of the fiber loops thereon, coating a latex on a back surface of the base fabric, and drying the latex not to slip off the fiber loops (hereinafter referred to as xe2x80x9ca tufting processxe2x80x9d).
The needle punched type of a carpet base material is manufactured by cutting synthetic fibers into an appropriate length, layering the fibers with a binder in a constant thickness, needling the layer to form a fiber plate like, and drying the binder. In such a needle punched type of a carpet base material, there is a carpet base material manufactured by layering the fibers with 5-20% wt of additional fibers having a low melting point such as olefin fibers instead of use of the binder, needling the layer to form a fiber plate like, and pressing and heating the layer to bond a part of the fibers not to come loose and slip off the layered fibers. Recently, use of this type of a carpet base material has been increasing.
In order to mold a three dimensional shaped carpet by use of those types of carpet base materials, two processes are required.
A first process thereof includes steps of coating a melt of polyethylene on a back surface of a carpet base material in a constant thickness and leaving the carpet base material at a room temperature for a moment. A second process thereof includes the steps of heating the carpet base material to 120-140xc2x0 C. in a furnace so as to soften the melt of polyethylene as though the melt is in a half-melting condition and pressing the carpet base material by use of a metallic die having a desired three dimensional shape.
Such two processes are required to mold a three dimensional shaped carpet, and this is because the step of coating the melt of polyethylene should be separated essentially from the step of pressing to mold the carpet.
While a three dimensional shaped carpet can be manufactured by according to such processes, a felt material is, in general, additionally adhered at a necessary part of the carpet in order to achieve a noise absorption.
As described bellow, there are several problems in the manufacture of a three dimensional shaped carpet used for an automobile by use of those types of carpet base materials.
Either type of carpet base materials require those two processes for molding a three dimensional shaped carpet, as described above. Thus, a manufacture of a three dimensional shaped carpet is inefficient. That is, there are many steps to mold a carpet in three dimension, and a large quantity of thermal energy is lost by repeating steps of heating and cooling. In addition, wasteful beginning products must be produced.
In the step of coating the melt of polyethylene on the back surface of the carpet base material, an extrusion coating by use of a T-die is required, and thus, large equipment is required and a large quantity of thermal energy is required when coating the melt.
In use of the tufted type of a carpet base material, two processes for treating a back surface of the carpet base material are required in order not to slip off fiber loops (or piles) provided thereon by a tufting process as described above. One process thereof includes steps of coating a latex on a back surface of the carpet base material (hereinafter referred to as xe2x80x9ca back coatingxe2x80x9d), heating the latex coated on the back surface of the carpet base material and changing the latex into a solid condition, and another process thereof includes a step of coating a melt of polyethylene on the back surface thereof. Assuming that coating the latex on the back surface of the carpet base material is avoided, the cost will be considerably reduced, but when the melt of polyethylene is coated on the back surface thereof without coating the latex, a melt of polyethylene will be percolated on a front surface thereof. Thus, those two processes are indispensable in the art and cause the fibers to lay on the front surface thereof so that the external appearance of the carpet is injured.
There are further problems caused when molding the carpet by use of such types of carpet base materials. The melt of polyethylene coated on the back surface of the carpet base material has a low specific gravity and is uniformly thin so that it is very light weight and is easy to handle, however, it is very inferior in several properties such as noise absorption, damping and thermal insulation.
Thus, in order to use those carpet base materials to manufacture a carpet used for an automobile which requires noise absorption, a damping property and a thermal insulation, in the art, a felt which has a relatively high density is adhered on a necessary part of a back surface of a carpet or, if necessary, vinyl acetate with a large quantity of calcium carbonate is coated over the back surface of the carpet. In addition, in order to achieve a damping property and noise absorption required for a high ranked passenger car, a thin nylon film is attached on the melt of polyethylene coated on the back surface thereof and a foamed body having partially different thickness and resiliency is molded on a surface of the film by molding a rim and the like thereon.
Such additional and several works are not desirable for mass production and increase the manufacturing cost, and thereby it is not practical.
Therefore, an object of the present invention is to provide a three dimensional shaped carpet used for an automobile and a method for manufacturing the carpet in which a thin polyethylene layer having a low specific gravity necessary to mold a carpet is not required.
Another object of the present invention is to provide a three dimensional shaped carpet used for an automobile and a method for manufacturing the carpet in which it is not necessary to carry out a back coating for preventing loosening and slipping off fibers of a surface material of the carpet.
Still another object of the present invention is to provide a three dimensional shaped carpet used for an automobile and a method for manufacturing the carpet in which a back surface of the carpet has a resilient foamed body layer having a partially different hardness.
Yet another object of the present invention is to provide a three dimensional shaped carpet used for an automobile and a method for manufacturing the carpet in which the carpet has a foamed body layer having a partially different thickness.
Yet still another object of the present invention is to provide a method for manufacturing the carpet used for an automobile in which it is not necessary to heat the carpet at a high temperature when molding.
In order to achieve those objects, a three dimensional shaped carpet used for an automobile according to the present invention comprises a surface material and a foamed body layer molded and connected in one with the surface material. On a back surface of the surface material a liquid foamable mixture is directly coated by a spray system, and the surface material is placed in a molding die comprising an upper portion and a lower portion which define a space inside the molding die corresponding to the three dimensional shape of the carpet. The surface material is clamped between the upper and lower portions when the liquid foamable mixture coated thereon has completed a gas reaction thereof but is still in a visco-elastic flowing condition, and thereby the foamed body layer, which is made from the liquid foamable mixture, having the three dimensional shape is molded and connected in one with the surface material.
A method for manufacturing a three dimensional shaped carpet used for an automobile according to the present invention comprises the steps of: coating a liquid foamable mixture directly on a back surface of a surface material of the carpet by a spray system; placing the surface material in a molding die comprising an upper portion and a lower portion having a space defined inside the molding die corresponding to the three dimensional shape of the carpet; clamping the liquid foamable mixture together with the surface material between the upper portion and the lower portion, when the liquid foamable mixture coated on the back surface of the surface material has completed a gas reaction thereof but is still in a visco-elastic flowing condition; and changing the liquid foamable mixture into a solid condition, and thereby a foamed body layer made from the liquid foamable mixture is molded and connected in one with the surface material through the back surface of the surface material.
The liquid foamable mixture is preferably selected from the group consisting of reactive resins such as a polyurethane foam resin and a polyurea foam resin, and it is desirable that the liquid foamable mixture is heated to 60-70xc2x0 C. and the heated liquid foamable mixture is sprayed.
By partially changing a volume of a space defined inside the molding die, the compressibility of a foamed body molded in the molding die can be partially changed. That is, the compressibility of a part of the foamed body molded in a small volume of the space is high and the compressibility of a part of the foamed body molded in a large volume of the space is low. In order to mold a partially thick foamed body layer, a partially large space is preferably provided in the molding die, and the liquid foamable mixture is coated thickly on a part of a back surface of the surface material corresponding to the large space by a spray system.
The surface material is selected from the group consisting of: a woven fabric and a knitted fabric made of a material selected from the group consisting of a natural fiber, a synthetic fiber, a chemical fiber and an inorganic fiber; a woven fabric formed of piles or fiber loops thereon by a tufting process; a knitted fabric provided with tufts formed of piles or fiber loops thereon by the tufting process; a nonwoven fabric; and a needle punched fabric.
Droplets of the liquid foamable mixture sprayed on the surface material by a spray system enter into a fiber structure of the surface material and are attached on a surface of each fiber of the fiber structure. The liquid foamable mixture attached thereon is immediately foamed by the gas reaction and is expanded, so that the liquid foamable mixture stays at a shallow part inside the surface material and is foamed without impregnating into a deeper part inside the surface material, and thereby the foamed body layer is connected in one with the surface material.
The surface material coated with the liquid foamable mixture is placed in the die comprising the upper and the lower portions and is then pressed between the upper and the lower portions when the liquid foamable mixture coated thereon has completed the gas reaction but is still in a visco-elastic flowing condition. Then, the three dimensional shaped carpet is formed.
The liquid foamable mixture used is a liquid reactive mixture consisting of a large quantity of water, so that the reaction can be accelerated by a heat of reaction of the liquid foamable mixture itself, and thus, it is not necessary to apply heat externally when molding the carpet. Also, moisture generated by the reaction migrates to the fibers of the surface material, and thereby the fiber structure of the surface material can be easily molded.
Moreover, the liquid foamable mixture is a high reactive composition and is heated and sprayed at 60-70xc2x0 C., so that the liquid foamable mixture is foamed and expanded immediately after attaching on the surface material, so that the viscosity thereof is rapidly increased. Thus, the liquid foamable mixture can be coated in fairly thick selectably at a necessary part of the surface material, and the thickness of the foamed body layer can be partially changed (into a thickness which is difficult in the art) by adjusting the volume of a space defined between the upper and the lower portions of the molding die.